1. Field of the Invention
The present invention relates to a technique of color restriction for printing or displaying by an image processing apparatus.
2. Description of the Related Art
In a full-color printer or a multi-functional printer (MFP), instead of full color or monochrome, color-restricted printing or copying which is in between the full color and the monochrome is known as two-color printing, mono-color printing and the like.
In full-color printing, printing is performed by using color materials (ink, toner, and the like) of four colors (black, cyan, magenta and yellow). On the other hand, in color-restricted printing, printing is performed by using color materials of two or three colors or by restricting colors. The number of colors is reduced so that consumption of toner can be reduced, and resource saving and cost reduction can be realized. Therefore, the color-restricted printing gradually started to be used mainly for office documents by users who are sensitive to their environments. In the following, printing by two colors, three colors or other color restriction is called color-restricted printing.
It is said that more than about 200 million people are partially color-blind or color-blind in the world population. Also, considering people having eye diseases, there are considerable amount of people having color vision deficiency. Although there are some types of partial color blindness and color blindness, there is a fear that particular people cannot recognize printed materials if printing is performed by only particular colors. To address such a problem, printing that supports color universal design (proposed by Color Universal Design Organization) is known.
There are conventional printers and the like that support the above-mentioned color-restricted printing. However, in the conventional printers, there is no flexibility in selecting colors for use for the color-restricted printing.
Also, in almost all of commercially available printers, even when only a color material of one color lacks, printing cannot be performed. This is similar to full-color printing. The reason is that printing of the preset number of colors cannot be performed normally due to lack of the color material. Therefore, even though color materials of other colors are remaining, any of the colors cannot be used in lieu of the lacking material. Thus, remaining color materials cannot be utilized efficiently.
Japanese Laid-Open Patent Application No. 2008-86011 (patent document 1) discloses a color printing method for selecting a correction method according to contents of an image in order to restore a color that a color-blind user can easily recognize. However, in this technique, color correction is performed when full-color printing is performed, and this technique does not target at images other than full color.
Similarly to printing, there are the same problems in displaying an image on a monitor except for lack of color material.